• Journal of Welding and Joining
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• v.3 no.1
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• pp.3-10
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• 1985

Lamellar tearing susceptibility and through-thickness tensile ductility have been investigated in $40kg/mm^2 and 50kg/mm^2$ class tensile strength steel plates in terms of cleanliness of non-metallic inclusion and welding condition. The plate which had 0.01% cleanliness of A-type inclusion (MnS) had 61% of the reduction of area in the through-thickness direction and did not show lamellar tearing. Lamellar tearing susceptibility decreased with increasing the preheat and interpass temperature. The plate which had 0.04% cleanliness of A-type inclusion did not show lamellar tearing under the condition of 75.deg. C of preheat and interpass temperature.

• Journal of Welding and Joining
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• v.10 no.2
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• pp.43-50
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• 1992

This study was aimed at resolving uncertainties about lamellar tearing initiation temperatures and studying the effect of nonmetallic inclusions on the tear initiation. In order to measure the lamellar tearing initiation temperature, the slice bend test was conducted in the temperature range of 20.deg.C to 425.deg.C on A572 Grade 50 and A588 Grade A steels. In addition, the weld restrain test was carried out to measure directly the tear initiation temperature with A572 steel. In slice bend tests, A572 steel showed the most susceptible region to lamellar tearing to be in the range of 100 to 300.deg.C, where the steel showed the minimum ductility. The observed tear initiation by the weld restraint test was to be in the range of 200to 300.deg.C. The tears became narrower and less rounded at the susceptible temperatures. It was confirmed in this study that lamellar teraring initiated during cooling from welding in the range of 200 to 300.deg.C and they were initiated by strain aging embrittlement.

• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.31-36
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• 2003

In case of this thick rolling-steel for a multistory building, a large oil-drilling structure, a large vessel, a bridge and so on, Lamella Tearing around the welded joint zone is the most serious problems. In order to prevent Lamella Tearing, not only is choice of material important, but also the comprehensive investigation for the structural design and the construction. The Lamella Tearing that is a staircase-shape occurs due to the contraction stress to the thickness direction of the plate and has the character that the cracks progress along the elongated inclusion by rolling. In general, because cracks occur at the heat affected zone and around HAZ, it is necessary to establish the safety and the confidence of the welded structure to restrain the welding defect such as Lamella Tearing. The mechanical approaches are the easier and more economical than the approaches of the material and the construction method. In addition, the appropriate welding profile and the optimum welding condition contribute toward the improvement of the productivity and influence on the standardization of the manufacturing technology.

• Journal of Welding and Joining
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• v.6 no.4
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• pp.44-53
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• 1988

The mechanical strengths of buried lamellar tears located near the weld toe in the welded tee joints were evaluated in terms of the loss of load carrying capacity as a function of tear area. In static loading, the load carrying capacity was significantly reduced when tear intercepted over 10% of the cross-sectional area of the welded joints. However, the welded joints containing buried tears still failed at stresses over the yield strength of the base metal in the through-thickness direction in spite of the presence of tears up to 20-25% of the area. Fatigue strength of welded joints containing tears markedly reduced with increasing tear areas. Lehigh lamellar tearing test used in this study to produce speicmens was described in detail. The load carrying cpapacity in static loading was influenced by the reduction of supporting area whereas that in fatigue loading was influenced by the stress-concentration effects of lamellar tears and the reduction of supporting area. In bend tests, the pre-existing lamellar tears always grew up toward the weld toe. However, in fatigue loading, cracks grew up and down simultaneously form both the weld toe and the top of lamellar tears because of stress concentration. In fatigue loading, delaminations and decohesion of inclusion/matrix interface generated in multipass welds provided crack propagation paths and enhanced crack propagation because the tips of delaminations and deconhesios acted as stress raisers.

• Journal of Welding and Joining
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• v.5 no.4
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• pp.1-11
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• 1987

라멜라 균열은 복잡한 현상이며 1960년대부터 연구가 되어 왔지만 국내에서는 그 중요성을 인정하면서도 연구가 되지 않았기 때문에 본 해설에서는 라멜라 균열에 대한 전반적인 이해를 돕기 위해, 라멜라 균열에 미치는 인자 및 비금속개재물, 형성기조, 개시온도 및 시간 그리고 방지책과 재료의 라멜라 균열에 대한 민감성을 평가하는 시험 방법과 용접구조물에서 라멜라 균열의 중요성 등을 기술하고저 한다.